The purpose of this project is to test the following hypotheses concerning the mammalian craniomandibular joint: 1) The magnitude and direction of force at the craniomandibular joint depends upon (a) the location of the bite point and (b) the orientation of forces applied to the mandible. 2) Differential contraction of the pinnate masticatory muscles (temporalis and masseter) occurs when the mandible and craniomandibular joint are loaded in various directions in order to reduce joint reaction forces and to reorient them through the bony portion of the joint. These hypotheses will be tested by implanting indwelling electromyographic electrodes in various portions of the temporalis and masseter muscles of domestic dogs (Canis familiaris) and bonding a rosette strain gage to several locations adjacent to the craniomandibular joint. Hypothesis 1 will be tested by training a dog to bite and pull on objects at various bite points along the tooth row so that bone strain and an approximation of force at the craniomandibular joint can be determined while the mandible is loaded under a variety of conditions. In order to test hypothesis 2, differential muscle activity and the magnitude and orientation of bone strain at the craniomandibular joint will be recorded simultaneously. Muscle activity will then be compared to the orientation of bone strain at the craniomandibular joint to see if differential contraction to reorient the forces at the craniomandibular joint occurs.